Field of the Invention
The invention relates to a measuring device for determining at least one measured quantity with at least one sensor device, at least one evaluation device and at least one interface. Here, the sensor device generates at least measurement information which is dependent on the measured quantity and the evaluation device determines at least one result value for the measured quantity. Furthermore, the invention relates to a measuring arrangement with at least one measuring device for determining at least one measured quantity and with at least one data device which is separate from the measuring device. Here, the measuring device likewise generates at least measurement information which is dependent on the measured quantity and determines at least one result value for the measured quantity. Furthermore, the measuring device and the data device are at least temporarily connected to one another. Moreover, the invention relates to a method for determining at least one measured quantity. The measured quantity is, for example, the flow rate, the liquid level, the pH value or the temperature of a medium.
Description of Related Art
In modem process automation, a plurality of measuring instruments is used to determine or to monitor measured quantities in order to monitor or control processes. In many measurements, specific information about the measurement medium, about the process, and in general, the background conditions is necessary. Occasionally, secondary measured quantities must also be considered since the quantity which has been determined directly during the measurement has several dependencies on different variable state quantities. In this respect, larger storage units for storing of parameters or information are optionally necessary. Furthermore, the computation formulas and evaluation algorithms which are necessary for achieving measurements that are as accurate as possible can be complex to use.
For example, if the flow rate of a flowable medium is being determined, depending on the measurement principle, for high precision measurements, the viscosity of the medium must also be included in the examination or evaluation. The same applies to the density of the medium when there is to be conversion between mass flow rate and volumetric flow rate measurements.
The implementation of complex computations or enabling large data storages increases the costs of the measuring devices and may collide with the application. In particular, measurements in areas at risk of explosion necessitate a limitation of the energy which is available for the measuring device. However, this runs counter to the fact that the implementation of longer algorithms with frequent data access to memory units is generally associated with an increased power demand.
German Patent Application DE 10 2006 016 381 A1 shows a measuring arrangement with at least one measuring instrument and an evaluation device which is arranged and configured separately from the measuring instrument. The measuring instrument generates a raw value from which the evaluation device determines the measured value. In one configuration, the evaluation device has access to an additional measuring instrument. The determined measured value is displayed by the measuring instrument via a display unit which belongs to the measuring instrument. The measuring instrument is therefore used to generate a raw value and to display the measured value obtained therefrom by a separate device.
A liquid level measuring instrument which can be used for any applications is described in German Patent Application DE 102 60 959 A1 and corresponding U.S. Pat. No. 8,065,912. A memory stores a plurality of parameter sets which are suitable for the different applications. An evaluation unit accesses the pertinent parameter set and computes the liquid level from the actual measurement signal.